added a way to enable/disable PHP support when parsing a YAML input via Yaml::parse()

PHP support when parsing a file has been disabled by default.
If you do need PHP support when parsing a YAML file, enable it via:

    Yaml::setPhpParsing(true);

As of Symfony 2.1, PHP support is disabled by default, and support will
be removed in Symfony 2.3.
added a way to enable/disable object support when parsing/dumping

By default, object support is disabled, and instead of throwing an
exception when an object is handled, null is returned.

If you do need object support, enable it via:

    Yaml::dump($data, false, true);

If you want an exception to be thrown in case an invalid type is handled
(a PHP resource or a PHP object), pass true as the second argument:

    Yaml::dump($data, true, true);

The same can be done when parsing:

    Yaml::parse($data, 2, false, true);
Added Yaml\Dumper::setIndentation() method to allow a custom indentation level of nested nodes.

YAML does not specify an absolute indentation level, but a consistent indentation of nested nodes only: http://www.yaml.org/spec/1.2/spec.html#space/indentation/

Projects that are generally using 2 spaces for indentation should be able to retain consistency with their coding standards by supplying a custom value for the new $indent parameter added to Yaml::dump(), or the new Dumper::setIndentation() method.

The new parameter is a backwards-compatible API addition and defaults to the previous default of 4 (which was changed from 2 via PR #2242 only recently).

Conflicts:
	src/Symfony/Component/Yaml/Dumper.php
	src/Symfony/Component/Yaml/Yaml.php
[Yaml] fixed default value
updated CHANGELOG for 2.0.22
update CONTRIBUTORS for 2.0.22
updated VERSION for 2.0.22
[Yaml] fixed typo
[DependencyInjection] fixed a bug in the YAML dumper where references where not converted to the @ notation
[Yaml] fixed unneeded BC break
bumped Symfony version to 2.0.23-DEV
[Yaml] fixed #6770
[Yaml] fixed #6773
merged branch ezzatron/yaml-block-chomping (PR #6785)

This PR was merged into the 2.0 branch.

Commits
-------

ab0385c [Yaml] fixed #6773

Discussion
----------

[Yaml] fixed parsing of blocks with 'keep' chomping indicators (2.0 branch)

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #6773
| License       | MIT
| Doc PR        | n/a

Also added a full set of tests for all combinations of literal/folded blocks and strip/clip/keep chomping indicators in both mid-file and end-of file positions.
merged branch ezzatron/yaml-negative-integers (PR #6784)

This PR was merged into the 2.0 branch.

Commits
-------

fea20b7 [Yaml] fixed #6770

Discussion
----------

[Yaml] fixed parsing of negative integers (2.0 branch)

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #6770
| License       | MIT
| Doc PR        | n/a

Note that an unrelated test fixture for large integers had to be changed to work on systems with 64-bit integer support because of the change from `assertEquals()` to `assertSame()`. Please see the diff for clarification.
[Yaml] fixed ignored text when parsing an inlined mapping or sequence (closes #6786)
[FrameworkBundle] fixed Client::doRequest that must call its parent method (closes #6737)
merged branch fabpot/client-fix (PR #6792)

This PR was merged into the 2.0 branch.

Commits
-------

ce38069 [FrameworkBundle] fixed Client::doRequest that must call its parent method (closes #6737)

Discussion
----------

[FrameworkBundle] fixed Client::doRequest that must call its parent method (closes #6737)

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #6737
| License       | MIT
| Doc PR        | n/A
merged branch fabpot/yaml-fix (PR #6790)

This PR was merged into the 2.0 branch.

Commits
-------

53ccc2c [Yaml] fixed ignored text when parsing an inlined mapping or sequence (closes #6786)

Discussion
----------

[Yaml] fixed ignored text when parsing an inlined mapping or sequence (closes #6786)

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #6786
| License       | MIT
| Doc PR        | n/a
[Security] PHPDoc in SecurityEvents